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野外露头浅钻取样分析发现,柯坪地区志留系下统柯坪塔格组的储层性质与塔北及塔中地区差别较大。柯坪地区的砂岩储层以粉细粒岩屑砂岩为主,处于晚成岩A2期,孔隙度主要为2%~6%,平均4.47%,渗透率主要为(0.01~0.1)×10-3μm2,平均0.06×10-3μm2,属于特低孔特低渗储层,而塔北及塔中地区以低孔低渗和中孔中渗为主。研究表明柯坪地区成岩压实、石英次生加大是储层物性的主控因素,储层经历长期深埋藏和短期浅埋藏,使成岩压实减孔率达30.4%;胶结作用所减少的孔隙量一般为1.5%~8%,致密胶结段可达10%~11%,石英次生加大所减少的孔隙量一般2%~4%,致密胶结段可达6%~8%;溶蚀作用及次生裂缝对储层物性改善不大,一般增孔量4%左右;成岩中后期强烈挤压构造运动对储层性质有重要影响。储层演化史表明晚二叠世、晚白垩世—早第三纪是油气聚集成藏期,随后遭后期构造运动破坏,油气逸散或发生氧化作用,柯坪塔格组含沥青砂岩即是这一过程的产物。
The analysis of the shallow outcrop sampling shows that the reservoirs in the Kepingtage Formation beneath the Silurian in the Keping area are quite different from those in the Tabei and Tazhong areas. The sandstone reservoirs in Keping are dominated by fine-grained litharic sandstones and are in the A2 stage of late diagenesis with porosity of 2% -6%, an average of 4.47% and permeability of (0.01-0.1) × 10-3μm2 , With an average of 0.06 × 10-3μm2, belonging to the ultra-low-porosity and ultra-low permeability reservoirs, whereas the low-porosity and low-permeability and mesoporosity in Tarim and Tazhong areas dominated. The results show that diagenetic compaction and quartz secondary growth in Keping area are the main controlling factors of reservoir physical properties. The reservoirs experienced long-term deep burial and short-term shallow burial, resulting in the compaction porosity reduction rate of 30.4% and the decrease of cementation The pore volume is generally 1.5% ~ 8%, the dense gel section up to 10% ~ 11%, quartz secondary reduction of reduced porosity generally 2% ~ 4%, dense gel section up to 6% ~ 8% The effect and secondary cracks have little effect on the physical properties of the reservoirs, with a typical increase of pore volume of about 4%. The strong compressional tectonic movement during the mid-late diagenesis has an important impact on the reservoir properties. The evolution of reservoir shows that Late Permian, Late Cretaceous-Early Tertiary are hydrocarbon accumulation and accumulation period, then destroyed by later tectonic movement, oil and gas evolve or oxidized. The karst sandstone in Kepingtage Formation is The product of this process.